I hear that a window can accomplish what you're trying to do. They're fairly cheap, and they even run on solar power!

I've used a trackball for almost 8 years. I originally used the Microsoft Trackball Explorer, but when mine died a new one was almost $200. So now I use a Logitech Cordless Optical TrackMan with the 'ergonomic' center-ball for all my gaming and absolutely love it. There was definately a learning curve to be able to play with the trackball after using a mouse for years.

I don't think I would call myself a "hardcore gamer" but I'm definately not used for target practice either.